1. Field of the Invention
The present invention relates to a current stimulator, particularly to a load-adaptive current stimulator fabricated in a low voltage IC process and able to output a stimulus voltage much higher than the supply voltage.
2. Description of the Related Art
Wafer foundries are flourishing in Taiwan. Without having to go far, IC industry of Taiwan is supported by the neighboring world-class wafer foundries and is growing fast with high technical burst power. IC industry of Taiwan has successfully developed various IC products. Further, the related organizations and manufacturers also integrate IC technology with biological technology to improve the medical environment and promote health of people.
Electric stimulus is an emerging medical technology and regarded as an alternative route to cure some illnesses thought incurable before, wherein current is used to stimulate a region to restore the function thereof. Advance in IC miniaturization makes it feasible to incorporate an intelligent bionic system in a single chip. Although different types of circuits can be integrated in a system-on-chip (SOC), there is still a problem for SOC current stimulators: current stimulators have to operate in a high voltage environment. When an IC fabricated in low voltage IC process operates in a high voltage environment, the voltage may be greater than the withstand voltage of the elements. In such a case, IC is likely to have problems of electric overstress, low gate-oxide reliability, hot-carrier degradation, and leakage current.
Besides, the load impedance varies with the region where the current stimulator is attached. Even in the case that the current stimulator is applied to the same region, the load impedance may vary with the materials of the electrodes and the duration of applying current stimulation. When the load impedance does not match, the stimulus current is no more effectively output.
Accordingly, the present invention proposes a current stimulator to overcome the abovementioned problems.